function teacherTestClass2(){
    var tom = new Teacher('Tom' , 21 , 2);
    var expectResult = 'My name is Tom. I am 21 years old. I am a Teacher. I teach Class 2.';
    (expectResult === tom.introduce()) ? console.log('teacherTestClass2 passed!') : console.log('teacherTestClass2 failed!');
} 

function teacherTestNoClass(){
    var tom = new Teacher('Tom' , 21 , null);
    var expectResult = 'My name is Tom. I am 21 years old. I am a Teacher. I teach No Class.';
    (expectResult === tom.introduce()) ? console.log('teacherTestNoClass passed!') : console.log('teacherTestNoClass failed!');
}

function teacherTestIntroduceWithNo(){
    var tom = new Teacher('Tom' , 21 , 2);
    var Jerry = new Student('Jerry' , 21 ,new klass(2));
    var expectResult = 'My name is Tom. I am 21 years old. I am a Teacher. I teach Jerry.';
    (expectResult === tom.introduceWith(Jerry)) ? console.log('teacherTestIntroduceWithNo passed!') : console.log('teacherTestIntroduceWithNo failed!');
}

function teacherTestIntroduceWithYes(){
    var tom = new Teacher('Tom' , 21 , 2);
    var Jerry = new Student('Jerry' , 21 ,new klass(1));
    var expectResult = 'My name is Tom. I am 21 years old. I am a Teacher. I don\'t teach Jerry.';
    (expectResult === tom.introduceWith(Jerry)) ? console.log('teacherTestIntroduceWithYes passed!') : console.log('teacherTestIntroduceWithYes failed!');
}

teacherTestClass2();
teacherTestNoClass();
teacherTestIntroduceWithNo();
teacherTestIntroduceWithYes();